JPH02298928A - Image pickup optical system - Google Patents

Abstract

PURPOSE:To properly adjust the quantity of light at the time of normal photographing and microphotographing and to reduce the size of a mechanism by arranging a material stop which has a light shield part whose maximum diameter is smaller than the maximum diameter of luminous flux capable of passing through a mechanical stop in an open state on an optical path nearby the mechanical stop. CONSTITUTION:In the image pickup optical system equipped with photographic lenses 1 and 2 and the mechanical stop, the material stop 4 which is variable in transmissivity with an electric field or magnetic field and a variable refractive index lens 5 as a liquid crystal lens are arranged nearby and behind the mechanical stop 3. In normal photography, light quantity adjustment and focusing are performed principally by the mechanical stop 3 and lens systems 1 and 2 and in microphotography, the light quantity adjustment and focusing are carried out principally by the material stop 4 and variable refractive index lens 5. The diameter (b) of the shield part 4a of the material stop 4 is smaller than the maximum diameter a0 of the mechanical stop 3 and a stop which is smaller than the minimum diameter a1 of the mechanical stop 3 is obtained by the material stop 4 in microphotography, so proper exposure and deep depth of field are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging optical system for a camera equipped with an illuminator that is capable of photographing (macro photographing) an object at a distance closer than a close distance (macro region).

[Conventional technology]

In recent years, cameras with built-in illuminators having an automatic focusing function have become popular, and cameras of this type are required to have relatively high precision, be compact, and be inexpensive. Therefore, when using an illuminator, the amount of light is adjusted by keeping the amount of light emitted by the illuminator constant and adjusting the diameter of the aperture, and in most cases, the aperture also serves as a shutter.

When performing macro photography using such a camera, it is necessary to use a strobe as an illuminator to prevent blurring during photography in order to ensure ease of use, and the amount of lens extension is extremely large. Furthermore, in order to adjust the amount of light, it is necessary to make the aperture diameter much smaller than in normal photography. However, since the aperture of this type of camera also serves as a shutter,
Accurate control of the aperture diameter is difficult, and if the aperture diameter is made smaller than a certain level, there is a risk of non-exposure.

For this reason, several improvement measures have been proposed as shown below.

The first method is to extend the lens to an appropriate position and fix it, fix the aperture diameter to a size that will give the correct exposure at a certain distance, deepen the depth of field, focus, and set the exposure according to the film. It relies on latitude, and is published in JP-A-58-152227, JP-A-59-149334, JP-A-56-151919, and JP-A-59-2010.
No. 27.

This is proposed in Utility Model Application Publication No. 61-88122 and the like.

As a second means, in addition to the diaphragm for normal photography, a diaphragm for close-up photography with a smaller diameter is attached, so that a stable small diaphragm can be obtained during close-up photography, as disclosed in Japanese Patent Laid-Open No. 59-2.
It is proposed in No. 01027.

As a third means, in order to accurately control the aperture diameter, it is widely known to use a physical aperture such as a liquid crystal aperture made of a member whose transmittance can be changed by electricity or magnetism. For example, one that uses polarized light (Utility Model 5)
4-154741) and one that does not utilize polarized light (Japanese Patent Application Laid-open No. 105125/1982).

[Problem to be solved by the invention]

However, the first method often has a mechanical diaphragm that also serves as a shutter, and operates at high speed, resulting in poor accuracy. Moreover, in order to prevent underexposure, you can set the aperture diameter to a large size to overexpose the macro area and rely on the latitude of the film to obtain a print with approximately the correct exposure, or you can shoot the macro area from a distance. I have no choice but to set it to . None of these are desirable for the camera's photographing accuracy itself.

Furthermore, the second method has the disadvantage that since two apertures are provided side by side, the mechanism becomes large and the camera becomes large.

Furthermore, the third means has a serious drawback in that the material constituting the physical aperture has greater scattering and absorption of light than optical glass, which deteriorates the performance of images during normal photographing. In addition, many physical apertures have poor light-shielding properties, and if the aperture is absolutely large compared to the light-shielding part, the effect of the aperture can be obtained, but when the ratio of the light-shielding part increases as the aperture is narrowed down, the light-shielding part becomes larger. Since the amount of transmitted light increases, the aperture effect that deepens the depth of field cannot be obtained, and when this amount of transmitted light becomes larger than the amount of light passing through the aperture, FM. , becomes 0.

On the other hand, a small illuminator that can adjust the amount of light emitted depending on the photographing distance is difficult to manufacture and is expensive, so it cannot be used.

In view of these problems, the present invention provides an imaging optical system that uses a physical diaphragm in addition to a mechanical diaphragm to appropriately adjust the amount of light during normal photography and macro photography, and that can maintain a compact mechanism. The purpose is to provide

[Means to solve the problem]

In the imaging optical system according to the present invention, a physical aperture whose transmittance can be changed by an electric field or a magnetic field is arranged on the optical path near the mechanical aperture, and the maximum diameter of the shielding part of the physical aperture is set when the mechanical aperture is opened. The diameter is smaller than the maximum diameter of the light beam that can pass through.

[For production]

During normal photography, exposure control is performed using a mechanical diaphragm, and during macro photography, exposure control is primarily performed using a physical diaphragm, and the depth of field can also be deepened.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

In the figure, Figure 1 shows the basic configuration of the imaging optical system.
．． 2 is a lens system arranged on the optical axis O, 3 is a mechanical diaphragm arranged between the lens systems 1 and 2,
The maximum diameter of the opening 3a is ao + the minimum diameter is al (
(See Figure 2). Reference numeral 4 denotes a physical aperture, such as a liquid crystal aperture, which is disposed close to the mechanical aperture 3. The maximum diameter of the shielding portion 4a is co, the maximum diameter of the aperture 4b is co, and the minimum diameter of the aperture 4b is Let cl be (see Figure 2). Also, b≧a
1≧C111. Reference numeral 5 denotes a variable refractive index lens, such as a liquid crystal lens, which is disposed behind the physical aperture 4 and close to the mechanical aperture 3, and its diameter is d, with d>co. Although the physical property aperture 4 and the variable refractive index lens 5 are diagrammatically shown separated in FIG. 1, they may be arranged integrally as shown in FIG. To further explain the structure of the component with reference to the cross-sectional view in FIG. 4, in the physical property aperture 4, 6.7 is a polarizing plate, 8 and 8' are a pair of transparent conductive layers connected to the power source S1, and 9 is a transparent conductive layer. 8,
TN liquid crystal sealed by a shielding part lO between 8′,
11 is a transparent substrate on the outer periphery of the shielding part 10. Further, in the variable refractive index lens 5, 12.13 is a transparent substrate, and 14.1 is a transparent substrate.
4' is a pair of transparent conductive layers connected to the power source S2, 1
5 is a TN liquid crystal enclosed by a spacer 16 between transparent conductive layers 14 and 14'.

In addition, the physical property diaphragm 4 and the variable index lens 5 are mechanical diaphragms 3.
It may be placed on either side of the front or rear side.

In addition, if the drive mechanism of the physical property aperture 4 or the variable refractive index lens 5 is made of an opaque member and needs to be placed close to the aperture 4 or the lens 5, the drive mechanism is replaced by the physical property aperture 4. If it is provided in the space between b and C6, which is the light-shielding part of , the influence on photographing performance can be minimized.

Also, during macro photography, it is easier to photograph objects in the macro area if the entire lens system is positioned at the closest focus position during normal photography, rather than at the infinity focus position during normal photography. It is convenient for Therefore, it is preferable that the entire lens system be extended to the closest photographing position by inputting a macro photographing signal or the like. The macro photography signal may be directly output to the subject in the macro area by the distance measuring device of the camera, or may be output by turning on a switch at the discretion of the photographer.

Also, for example, by a macro photography signal or by a mechanical aperture 3.
When the diameter of the aperture 3a is narrowed down to a predetermined size, the physical property aperture 4. A method is adopted in which the variable refractive index lens 5 is driven. Note that the macro photography signal may be output by moving the lens system to the closest photography position.

This embodiment is constructed as described above, and its operation will be explained next.

First, during normal photographing, focusing is performed by mechanically moving the lens systems 1 and 2, and the variable refractive index lens 5 is not driven. Further, the amount of light is mainly adjusted by the mechanical diaphragm 3, and the physical diaphragm 4 keeps the shielding part 4a and the opening part 4b in a transmitting or shielding state.

In terms of the amount of light, it is advantageous to keep the physical aperture 4 in the transmitting state, but even if it is in the shielding state, the diameter of the shielding part 4a in the shielding state is less than the aperture 3a of the mechanical aperture 3. There is no practical problem if it is sufficiently small. When the physical property diaphragm 4 is kept in a shielded state, if it is configured to have a diameter of bad, no matter what value the refractive index of the variable refractive index lens 5 has, it will not affect photography. In addition, when the physical property diaphragm 4 is kept in a transmitting state, the refractive index of the variable refractive index lens 5 is
The refractive power of the lens 5 is made equal to the refractive index of the transparent member supporting the lens 5, so that the refractive power of the lens 5 does not affect the imaging performance.

Further, during macro photography, the entire lens system is moved to the closest distance photography position by inputting a macro photography signal, etc., and focusing is performed mainly by driving the variable refractive index lens 5. Further, since the strobe is forced to emit light, the opening 3a of the mechanical diaphragm 3 is fixed to a predetermined minimum diameter a. The amount of light is adjusted mainly by driving the physical aperture 4, which is determined in accordance with the subject of the aperture 4b, while a portion of the shielding portion 4a that is closer to the optical axis than the diameter thereof blocks light. The portion closer to the optical axis than the required diameter c' (co≧C′≧C1) allows light to pass through.

Further, the light amount adjustment will be further explained based on FIGS. 5 and 6. Now, the shape (diameter an) of the opening 3a when the mechanical diaphragm 3 is open is made circular for convenience, similar to the shape (diameter b) of the outermost shielding part 4a of the physical property diaphragm 4, and its area is respectively A.
ao and Ab, the transmittance of the portion between the diameter a0 of the opening 3a and the diameter of the shielding part 4a is 1, and the transmittance inside the shielding part 4a is ρ. For simplification, let us assume that the transmittance inside the minimum aperture (diameter CO) of the aperture 4b of the physical property aperture 4 is the same as that of the surrounding area (ρL), then Aa, = π3o''
/4. Ab=πb''/4.

Also, when comparing the light amount LN+L of the conventional example in which normal photography and macro photography are performed only with a physical lens and the present invention in the open state during normal photography (in this case, the shielding part 4a is in the transmitting state), L , (Conventional? ri・AalOr”Ka
+'/4"O+sL, (invention) (8 ml -Ab)
・l+^b'h=x (a+ '-b')/4
+rb' /4・ρt, and the difference is -L1□ (i-fl+) (Aal -A
b)・r(1-ρtl (a+'-b')/1.

From the above equation, it can be understood that if the diameter is smaller than the diameter a0, the amount of light in the open state during normal photography can be increased. It is clear that the smaller the aperture, the more the light amount can be increased, but the size of the aperture is limited by the condition (b≧a+≧C0) for obtaining a focusing effect during macro photography.

In any case, the area Ab of the aperture of the physical aperture 4 is determined by various factors, but the area Ab of the shielding part 4a of the physical aperture 4 is equal to the aperture area A of the mechanical aperture 3 when it is open.
It can be seen that if it is smaller than a o, the amount of light in the open state during normal photography can be increased.

, Also, the size of the diameter is a with respect to the diameter a0. When the amount of transmitted light changes from 0 to 0, the relationship with the transmittance ρ is shown in FIG. 6, and the smaller the diameter, the more the amount of transmitted light increases.

In the figure, (ao'b')/a,'' is a formula for expressing the change in diameter as a simplified value (0→1) on the horizontal axis of the figure.

Further, the aperture effect for obtaining a deep depth of field during macro photography will be explained with reference to FIG.

When it is necessary to narrow down the aperture 4b of the physical aperture 4 to the minimum diameter CI, the amount of light passing through the aperture 4b is determined by Fla, diameter b% C, and the shielding part 4a between (and inside the aperture 3a of the mechanical aperture 3) ) (the shaded area in Figure 7) is F 6
If ul, then Fl.

In this case, there is no filtering effect. Therefore, F au+ < F Is (
1), especially F 6111 ≦F+-/2 (2
), which increases the depth of field and provides a clear image. Furthermore, the values of the diameters a1 and co are limited by equation (2).

To explain this more specifically, the area of the square opening 3a of the mechanical diaphragm 3 is A a +
= a + ' / 2 '' (3) Area of the circular opening 4b of the physical property aperture 4 Ac + = πc + '' / 4 ...
Assuming (4), the above equation (1) becomes (AaI Aal)ρ≦AC3 (1)', and by substituting equations (3) and (4) into this, it becomes. Moreover, the above formula (2) is (Aal-Ac1)ρ≦A c , / 2 ...
・(21', plus (3), (4), +5)
By substituting the formula, we get: The relationship between al and cI for obtaining a better narrowing down effect is determined.

Note that it is better not to arrange a member that reduces the transmittance of light, such as a polarizing plate, inside the diameter CI of the aperture 4b of the physical property diaphragm 4.
The amount of light transmitted through the area Aal can be increased.

In addition, a shielding portion 4a-1 (
(see Figure 8) is made of a material with a large shielding effect such as iron, the area Aa in the above equations (1)' and (2)' is the area between this part 4a-1 and the opening 3a of the mechanical diaphragm 3. Common part 3
Area A of b. The value after subtracting will be applied.

In addition, if this shielding part 4a-1 is a member that transmits light to some extent, then if lO, a narrowing effect corresponding to the above formula (2) or (2)' can be obtained. .

As described above, according to this embodiment, during normal photography, the mechanical aperture 3 and the lens systems 1 and 2 adjust the light amount and focus, and during macro photography, the physical aperture 4 and the variable refractive index lens 5 mainly adjust the light amount. Adjustment and focusing are performed. Especially in the case of macro photography, the diameter of the mechanical diaphragm 3 is the minimum diameter a, so the maximum diameter of the shielding part 4a of the physical property diaphragm 4 is larger than al, and the minimum diameter C2 of the aperture 4b is a,
Although it needs to be smaller, the shielding part 4 of the physical property aperture 4
The diameter a should be at least smaller than the maximum diameter a0 of the mechanical diaphragm 3, so that the physical diaphragm 4 can be made smaller.

Further, during macro photography, a stable small aperture smaller than the diameter al can be obtained by the physical aperture 4, and proper exposure and a deeper depth of field can be obtained without the risk of underexposure.

Note that if the light shielding ability of the shielding portion 4a of the physical aperture 4 is low, a deeper depth of field cannot be obtained, but it is possible to sufficiently adjust the amount of light and proper exposure can be obtained.

Even during normal shooting, if the aperture diameter becomes small enough,
The light amount can be adjusted and focused using the physical property diaphragm 4 and the variable refractive index lens 5.

Furthermore, in the cameras targeted by the present invention, the shutter often serves as an aperture, and in that case, the maximum diameter a0 of the aperture 3a of the mechanical diaphragm 3 is the maximum aperture diameter of the shutter, and the minimum diameter a1 is the exposure diameter. The minimum opening diameter of the shutter may be used.

In the above description, two types of lenses, the lens system 1.2 and the variable refractive index lens 5, are provided, but only the normal lens system 1.2 may be used.

Hereinafter, a first embodiment with numerical limitations will be described in detail.

! The configuration of this embodiment is shown in the sectional view of FIG.
Each diaphragm 3, 4 and variable index lens 5 are constructed in the same manner as shown in FIG.

In the figure, the mechanical diaphragm 3 also serves as a shutter, and the aperture 3
The minimum aperture system a of a is controlled to a size between F'so,to and 16. A liquid crystal aperture (polarizing plate, TN liquid crystal, polarizing plate) that uses polarized light is used as the physical aperture 4, and its outer diameter is larger than the diameter of Fso and 10 (and FNo.
, 9 is set to such a size that the light beam inside the radius will definitely pass through the liquid crystal aperture 4. Further, the liquid crystal diaphragm 4 is designed to be able to control the aperture value within the range of FNo. 16 to 64.

A liquid crystal lens is used as the variable refractive index lens 5 (the polarizing plate is shared with the liquid crystal aperture 4, and the liquid crystal lens layer is a single layer, see Figure 4).
, whose outer diameter is thicker than FNo. 16 (and Fso
, a radius of 1.145) is large enough to allow a light beam with a diameter of 15 to pass through without being vignetted.

- Also, the refractive index of the case in which the liquid crystal is sealed is set to 1 and 5, which corresponds to the value of the refractive index n0 of the liquid crystal.

In the data below, r++r! y ... is the radius of curvature of each lens surface, etc., d1 + dt * ... is the interval between each lens surface, etc., nl + nt + ... is the refractive index of each lens, etc., sill, s2 ．． ... is the Atsube number of each lens, etc.

1st surface rt ~10.928, cL =2.657, 1
1 = 1.6968゜ν, ~55.5, 2nd surface r t ~32.438, d - = 1.043
, 3rd surface rs = -52,226, dx = 1.022, n
l = 1.7552゜νI ~27.5, 4th surface rt ~24.328. d, =1.533, 5th surface r, =oo (aperture), d, =0.269, 6th surface
Surface r s =”, ds =0.480, ns
=1.5000°, =57.5, LCD aperture, 7th surface r t ”32.786. d t =0.020,
n? =1.5~1.7.

shi, =30~25, liquid crystal lens, 8th surface r*=”, ds =0.500,
rl+ =1.5000.

si, =57.5, 9th surface r s =21.906. d e =4.831,
n Q =1.6237°ν* =47. L 10th surface r II) = -29,369, d +o = 6.175,
11th surface r z = -7,218, d z = 2.044, n
z = 1.4922゜ν, , = 57.5, 12th aspherical surface, lens total length 20.674, aspherical surface R = -14,761, A, = 0.26946
Xl0-'.

A, =-0,92516xlO-'', As =0.
10629 xlO-'.

A1°=0.64435Xl0-”.

Next, the operation of the camera in this embodiment will be explained by limiting it to focusing and exposure.

During normal shooting, the liquid crystal diaphragm 4 is set to a transmitting state, and the refractive index of the liquid crystal lens 5 is set to 1.5, which is equal to the refractive index of the case, so the amount of light decreases slightly due to the polarizing plate.
Paraxially and aberrationally, both members 4.degree. 5 are in the same state as if parallel plane plates were disposed.

During macro photography, the input of the macro photography signal causes the entire lens to move out to the closest photography position (object-image distance 100100O, and if the subject is closer than the closest photography position) , liquid crystal lens 5
Focusing is performed. Further, the shutter is set to open to a predetermined minimum aperture diameter a1 regardless of the amount of exposure, and the amount of exposure is adjusted by the liquid crystal diaphragm 4.

The refractive index of the liquid crystal lens 5, the main paraxial amount of the photographic lens,
The aperture diameter etc. at the object-image distance are shown in the table below. Note that the transmittance of this liquid crystal aperture 4 is 30%.

LCD lens! II Focal length Front/rear focal position Object 1 distance Optimal aperture radius (14th 111.5H1
l 3S, On -4139g/15J
I IHl, 1.554 (11 formula 1
) IJIIIll 31.765-37
．． 131/+1516 353. G...! 31
I liquid crystal aperture) 1゜70110 2107g
-34m1/11.111! ! ! 4. !
, L5 Aperture (Liquid crystal diaphragm) As an effect of this embodiment, the combination of the liquid crystal diaphragm 4 and the liquid crystal lens 5 can share a polarizing plate, so there is no waste in the configuration, and each electrode is transparent, so the luminous flux during normal shooting is reduced. One example is that it has little impact on

Also, the light loss is (2, 8/9)" 0, since the transmittance of the liquid crystal lens part is 30% when the mechanical diaphragm 3 is open and the FNo. is 2.8 during normal shooting. .7 = 0.06775, which is about 7%, which is much smaller than the light amount loss of about 70% when a polarizing plate is used over the entire effective diameter as in the prior art.

If the liquid crystal lens 5 is of a type that does not require a polarizing plate, such as one that does not require a polarizing plate, such as one that is composed of a plurality of liquid crystal lenses in which the orientation directions of the liquid crystals are perpendicular to each other, the liquid crystal aperture 4 is also of a type that does not use a polarizing plate. By doing so, an increase in the amount of transmitted light can be expected. In this case, astigmatism occurs, but since the liquid crystal lens 5 is used only in a stopped-down state, the depth of field becomes substantially deep, and the influence of astigmatism can be reduced.

〔Effect of the invention〕

As described above, according to the imaging optical system according to the present invention, apart from the mechanical diaphragm, a physical diaphragm is arranged whose maximum diameter of the light shielding part is smaller than the maximum diameter of the light flux that can pass through when the mechanical diaphragm is opened. The amount of light can be adjusted appropriately during photographing and normal photographing, and a stable small aperture can be obtained without the risk of unexposed light due to the physical aperture during macro photography. It may also be possible to obtain a greater depth of field. Furthermore, since the physical aperture is small, it is easy to manufacture, the manufacturing cost can be reduced, and the size of the camera can be kept compact.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of the imaging optical system according to the present invention, Fig. 2 is a schematic plan view of a mechanical diaphragm, a physical diaphragm, and a variable refractive index lens, and Fig. 3 is a schematic plan view of a mechanical diaphragm, a physical diaphragm, and a variable refractive index lens. 4 is a schematic cross-sectional view of the physical aperture and the variable refractive index lens, FIG. 5 is a diagram showing the relationship between the aperture of the mechanical aperture and the shielding part of the physical aperture, and FIG. In the figure, a diagram showing the relationship between the diameter of the shielding part of the physical aperture and the amount of transmitted light, FIGS. 7 and 8 are diagrams for explaining the aperture of the mechanical aperture and the light transmitting part of the shielding part of the physical aperture, FIG. 9 is a block diagram of the first embodiment with limited numerical values. 1.2...Lens system, 3...Mechanical aperture, 3a
...Aperture, 4...Physical property diaphragm, 4a...Shielding part. Fang 3 Figure IP 4 Figure 1-5 Figure 31-6 (b = ago) Procedural amendment (voluntary) 1. Indication of case Japanese Patent Application No. 1-119554 2. Title of invention Imaging optical system 4. Agent 196, Shinbashi 5, Minato-ku, Tokyo 105, Contents of amendment (1) On page 4, line 19 of the specification, 'F No is set to 0' is corrected to 1, where rF No is close to the open value. (2) "rTN liquid crystal" on page 7, line 9 of the specification is corrected to "nematic liquid crystal." (3) "r, -21,9" on page 19 of the specification cylinder, lines 4 to 11
06, ``Page 12'' is corrected as stated below. 'ri='', do=0.1OO1 1st O surface rlo=21.906, d1o=4.831,
n1o=1.6237゜ν1゜=47.1, 11th surface r z=-29,369, d z=6.175, 12th surface
Surface r 1g=-7,218, d+g=2.044,
n l! =1.4922゜ν1□=57.5, Page 13 1 (4) Figure 9 of the drawings is corrected as attached. that's all

Claims (1)

[Claims] In an imaging optical system equipped with an imaging lens and a mechanical diaphragm,
A physical aperture whose transmittance can be changed by an electric field or a magnetic field is arranged close to the mechanical aperture, and a maximum diameter of a shielding portion of the physical aperture is smaller than a maximum diameter of a light beam that can pass through when the mechanical aperture is opened. An imaging optical system comprising: